1. Field of the Invention
The present invention relates to an electronic device having a radio communication function for executing data communication with another device and a connection control method.
2. Description of the Related Art
In recent years, radio communication systems in personal areas, such as the IrDA, Bluetooth, and Home RF, have received a great deal of attention. Particularly, the Bluetooth and Home RF are advantageous in omnidirectionality and high transmittance as compared to an infrared communication scheme such as the IrDA and are promising systems in the near future. The Bluetooth is a short-distance radio communication standard and realizes radio communication within the range of 10 m or 100 m using the 2.4-GHz ISM (Industrial Science Medical) band.
A radio communication system such as the Bluetooth or Home RF can simultaneously connect a plurality of devices. In addition, as one of characteristic features, the transmission distance is as long as, e.g., 10 to 100 m as compared to an infrared communication scheme such as the IrDA. Although this can improve the convenience, the user must make sure to sufficiently ensure the security and privacy of the radio communication system because the system can easily be accessed from the outside.
As a general security system for a radio communication system, a security system is known, which is used an electronic key and inhibits continuous use of a single key to improve the security, thereby increasing the safety against loss or theft.
The Bluetooth employs the following security scheme using user authentication.
User authentication in the Bluetooth is managed by a unique authentication password set in a device and an encryption key created by the authentication password and an ID (a 48-bit address issued and managed by the IEEE) unique to the device. The authentication password is called a PIN (Personal Identification Number) code and formed from an arbitrary character string. The encryption key is called a link key and also used for data encryption as well as user authentication.
Assume that a device A accesses a device B.
If the devices A and B are to be connected for the first time, the device A must input the PIN code of the device B. If it is determined that the PIN code input from the device A is correct, the device B determines that the authentication is successful and then creates a link and permits connection. At this time, the device B generates a link key of the device A by, e.g., multiplying the PIN code of its own and the ID of the device A by a random number, and stores the link key in the link key table together with the ID of the device A. To generate the link key, the ID of its own and the PIN code of the other party with which the link key is exchanged are also used.
On the other hand, if the device A is used to be connected to the device B in the past, the link key of the device A has already been registered in the link table. Hence, authentication using the link key is executed without inputting the PIN code.
There are a variety of devices using the Bluetooth. One of them is a line connection device called a modem access point. This modem access point has a public line connection function. When the communication function of the Bluetooth is added to the device, it can be connected to another Bluetooth device by radio. Hence, when the modem access point is accessed from an external device by radio, the external device can be connected to a public line to use the Internet or the like without connecting a modular cable. In this case, the above-described authentication using a PIN code or link key is done in accessing the modem access point, and only an external device for which it is determined that the authentication is successful can be connected to the modem access point.
However, if the PIN code of the modem access point is known by a person other than the authentic user by some means, that person may illicitly access the modem access point using the PIN code. For a modem access point, since the user is charged for use of a public line upon connection to the line, an illicit access poses a serious problem.
In addition, normally, a modem access point is installed at an unnoticeable place, and its power is often always ON. For this reason, the manager may not be aware of an illicit access from the outside to the modem access point.